The present invention is directed to a process for separation of blood into its components through density centrifugation, wherein in a first separation stage with a monitored phase boundary, the blood is coarsely separated into at least two phases, of which a first fraction consists primarily of blood cells and the second fraction primarily of thrombocyte-rich blood plasma, and wherein in a second separation stage, one of the fractions is further separated for the purpose of obtaining a concentrate of one blood component. The invention further concerns a device for separation of blood into its components through density centrifugation with a first separation stage, the separation chamber, to which the blood to be separated may be delivered on the input side via a blood pump, wherein the blood is coarsely separated into at least two phases, of which the first fraction consists primarily of blood cells and the second fraction primarily of thrombocyte-rich blood plasma, and which has means for detection of the phase boundary between the two fractions with a second separation stage, the collection chamber, to which the thrombocyte-rich blood plasma may be delivered via a plasma pump, and in which this fraction may be further separated for the purpose of obtaining a concentrate of one blood component, and with a program controller for operation of the device including the adjustment of the pump speed of the plasma pump. Preferably, the thrombocyte-rich blood plasma fraction is further separated in the second separation stage for the purpose of obtaining a thrombocyte concentrate.
Such devices have become known, for example, through the cell separator of the applicant Fresenius AS 104, of the Baxter company CS 3000, or the Cobe company Spectra. Specific blood components which are delivered to the patient are needed for the treatment of patients with certain diseases. Thus, for example, thrombocyte concentrates are needed for the treatment of thrombocytopenic patients. For this purpose, the blood of a donor, connected to an extracorporeal circuit, is subjected to density centrifugation in a blood centrifuge, and separated into its components. During this blood separation, in a first stage the blood is coarsely separated into two phases, i.e., into a dark red cell concentrate fraction, which at first consists primarily of erythrocytes, and into a clear, yellowish fraction which consists primarily of thrombocyte-rich blood plasma. The position of the boundary between the two phases is monitored by a detector device and regulated, for example, by a plasma pump. The term "high phase boundary" is used when the volume of cells outbalances the volume of cell-rich plasma, and the term "low phase boundary" is used in the opposite case. In known processes for obtaining thrombocyte concentrates, in the usual mode of operation, after reaching the desired position, the position of the phase boundary is kept constant during the entire duration of the separation.
If one wishes to obtain a thrombocyte concentrate, the thrombocyte-rich plasma is separated in a second stage into thrombocyte-poor plasma and the desired thrombocyte concentrate. The thrombocyte concentrate is used for the treatment of the patient; the remaining components of the blood are recombined and retransfused to the donor.
A standard thrombocyte concentrate, consisting of approximately 3 to 4.times.10.sup.11 cells, should be obtained with the shortest possible separation period, with the highest possible yield, and the lowest possible contamination by leukocytes. In a foreign organism (in this case, the patient), leukocytes trigger defense mechanisms which can sharply restrict the effectiveness of preparations administered subsequently.
Lymphocytes, a subfraction of the leukocytes (which are the determining factor in triggering the defense mechanisms), and thrombocytes cannot be separated from each other with certainty by centrifugation according to the known processes because of the small difference in size. Consequently, according to the prior art, to assure avoidance of immunization a thrombocyte concentrate is additionally filtered to separate out the leukocytes, before it is transfused to a patient. Comparable measures are performed with other blood components.
Consequently, with the known process an additional processing step in another separation device is necessary, whereby time and cost are disadvantageously increased, also with regard to maintaining sterility.
The object of the invention is to design a process and apparatus such that a blood component, in particular a thrombocyte concentrate, which has extremely low contamination and consequently does not have to be further filtered, can be obtained directly.